It is commonly known that the baths of electrical furnaces are built up from a lining forming a bottom and walls, a metal jacket, and a sealing layer interposed between the jacket and the lining. The baths of such electrical furnaces are provided with openings for discharging slag and a resulting product. The linings of the electrical furnace baths are subjected not only to intensive thermal exposure, but also to corrosion caused by the melted slag. The foregoing conditions cause special problems associated with the protection of these linings from the action of highly aggressive acid melted slags which are typical for the reduction smelting of ferronickel.
Usually for the purpose of enhancing the resistance of the electrical furnace linings intended for operation in the presence of melted slags, these linings are manufactured with the use of magnesite materials, in particular, magnesite or chromomagnesite refractory bricks (see for example "Osnovy metallurgii" ("The Essentials of Metallurgy"), Moscow, 1961, vol. I, part I, pp. 78-82), or a refractory mass composed of magnesite powder and refractory clay (see U.S.S.R. Inventor's Certificate No. 104437 issued Nov. 31, 1956). Such linings of magnesite materials are capable of successfully withstanding comparatively low specific electrical furnace outputs, but, however, should the level of specific output increase up to 70-90 kW/m.sup.2, these linings tend to break down from corrosion, particularly in the zone of action of the melted slag.
There are known a number of methods for the protection of electrical furnaces from corrosion effects produced by the melted slag which feature freezing a coat of slag lining onto the internal surface of the lining. This is ensured by withdrawing the flow of heat from this surface by means of cooling. There are different designs for electrical furnace baths operating on this principle.
Known in the prior art are ore-smelting electrical furnace baths in which the lining refractory brickwork in the melted slag zone comprises a plurality of built-in water-cooled elements mounted at a comparatively short distance from the internal surface of this lining, such elements usually include jackets (U.K. Accepted Application No. 1444507 issued Aug. 8, 1976) or coils (U.S.S.R. Inventor's Certificate No. 491012 issued Nov. 5, 1975). In such baths the internal surface of the lining in the melted slag zone develops a sufficiently thick coat of slag lining. However, the built-in water-cooled elements located near the internal surface of the lining tend to cause the risk of developing uncontrolled burn-outs which are attended by the inrush of water into the bath and, as a consequence, by complete breakdown. Furthermore, the provision of numerous inlets and outlets for the circulation of water in such electrical furnace baths makes the task of sealing these baths highly difficult. If, however a complete sealing is not provided, the economic efficiency factors of the electrical furnace operation tend to drop owing to the suction of air. While reviewing the designs of the electrical furnace baths under consideration it should be also taken into account that the provision of built-in water-cooled elements considerably increases the labour and the time required for maintenance and repair.
Also in the prior art is an ore-smelting electrical furnace bath for the smelting of ferroalloys, which comprises a lining made with the use of carbonaceous refractory blocks, a metallic jacket provided with means for external cooling and a sealing layer interposed therebetween (see "Futerovki ferrosplavnykh pechei" (The linings of Ferroalloy Furnaces") in the collection of articles "Information Review of the General Research Institute of Ferrous Metals", Moscow, 1976, Series No. 5, second issue). The above-described electrical furnace bath is closely related to the subject of the present invention. It is comparatively simple in design and in repair, reliably sealed and provides fair conditions for the formation of a protective slag lining coat on the internal surface of the lining.
However, the relatively high resistance displayed by the bath lining of this prior art electrical furnace ensures only up to specific outputs in the range from 100 to 120 kW/m.sup.2. This does not allow increasing the output of the electrical furnace and, as a consequence, its efficiency. The bath under consideration makes use of carbon blocks for the carbonaceous refractory blocks. But as the calculations and the experimental investigation data have revealed, with a thickness of carbon blocks ensuring the required mechanical strength and with any material for the sealing layer it becomes impossible, should the level of output exceed of the aforesaid range, to withdraw the desired amounts of heat for freezing a coat of slag lining with a thickness sufficient for the provision of protective functions.
It is an object of the present invention to provide an ore-smelting electrical furnace bath which has improved efficiency levels at the expense of increasing the overhaul period of the lining of the electrical furnace with a high specific output.
Another object of the invention is to provide an ore-smelting electrical furnace bath of the above character featuring safety in operation.
Still another object of the invention is to provide an ore-smelting electrical furnace bath of the above character which has such a fairly simple design that results in a considerable decrease in the consumption of labour as well as in the time required for its maintenance and repair.
Other objects of the present invention will become apparent from the following detailed description of its embodiments.